Process for the production of low silicon, medium-to-low carbon ferromanganese



17, 1967 E. F. BAUER, JR.. ETAL ,6

- PROCESS FOR THE PRODUCTION OF LOW SILICON, MEDIUM-TO-LOW CARBONFERROMANGANESE 2 Sheets-Sheet 1 Silicon Reducing Ager wf Filed March 25,1965 Slag Ferromanganese M n Ore Llme Carbon INVENTORS EDWIN F.BAUER,JR. KUR

TORNEY 1967 2:. F. BAUER; JR.. ETAL 3,34

PROCESS FOR THE PRODUCTION OF LOW SILICON, MEDIUM-TO-LOW CARBONFERROMANGANESE Filed March 23, 1965 2 Sheets-Sheet 2 Gas Mixing 3 N Belguw INVENTOR KURT O. RIEDER BY ,WM/Mfi M ATTORNEY EDWIN F. BAUERSZJR.

United States Patent 3,347,664 PROCESS FOR THE PRODUCTION OF LOWSILICON, MEDIUM T0 LOW CARBON FEUMANGANESE Edwin F. Bauer, Jr., NiagaraFalls, and Kurt 0. Rieder,

Tonawanda, N.Y., assignors to Union Carbide Corporation, a corporationof New York Filed Mar. 23, 1965, Ser. No. 442,019 2 Claims. (Cl. 75133)The present invention relates to the production of ferromanganese. Moreparticularly, the present invention relates to an improved ladle processsuitable for the production of medium-to-low carbon ferromanganese.

At the present time, ladle processes for producing ferromanganese areknown and practiced commercially as exemplified in the disclosures ofUS. Patent 3,074,793 to Kuhlmann and US. Patent 3,138,455 to Carosellaand Chynoweth. Both of these patents describe the reaction of a melt ofoxidic manganese-containing material with a silicon reducing agent in aladle to provide ferromanganese alloy and a manganese-containing slag.In general, the processes of the aforementioned patents are highlysuccessful in producing high quality ferromanganese alloys. However, inorder to increase the reduction of the manganese values from the meltand thus obtain high manganese recoveries, it is frequently necessary torepeatedly pour the ladle contents from one ladle to another to therebyincrease contact between the metal and oxidic phases, and hence promotethe reduction reaction. Up to the present time, repouring has beenconsidered the optimum manner of promoting the interraction of largequantities of molten materials in ferromanganese production andconsiderable equipment has been designed and constructed from thispurpose. However, the extent to which repouring can be utilized islimited by the relatively long handling times involved and theconcurrent cooling effect which can result in the freezing ofsignificant amounts of material in the ladles. Consequently, repouringmust often be discontinued before the reaction between the oxidic andmetal phases has reached equilibrium and before the optimum amount ofmanganese has been reduced from the oxidic phase.

It is therefore an object of the present invention to provide animproved ladle process for the production of ferromanganese in whichre-pouring of molten material from one ladle to another is madeunnecessary.

It is a further object of the present invention to provide an improvedladle process for the production of low silicon, medium-to-low carbonferromanganese from oxidic manganese material wherein greater quantitiesof manganese are reduced from the oxidic melt or slag than has beenpreviously attainable on an industrial scale.

Other objects will be apparent from the following description and claimstaken in conjunction with the drawing in which FIGURE 1 shows a diagramof a ladle process in accordance with the present invention,

FIGURE 2 shows a ladle particularly suited for the practice of thepresent invention and FIGURE 3 shows a graph comparatively illustratingadvantages of the present invention.

A process in accordance with the present invention comprises the stepsof: 1) preparing a melt of oxidic manganese-containing material in whichthe amount of oxygen combined with manganese is no greater than aboutthat represented by the formula Mn O (2) transferring the melt to aladle and also introducing into the ladle a molten silicon reducingagent, such as silicon metal or a silicon-containing manganese-ironalloy, to provide a molten metal phase in the lower portion of the ladleand molten oxidic manganese-containing material floating on the metalphase (3) introducing gas under pressure into the molten metal phase tocause turbulence in the metal phase to the extent that molten metal iscontinually forced upward through the oxidic material and falls backdownward through the oxidic phase and (4) continuing the introducing ofgas until the metal phase has a desired ferromanganese composition.

In the practice of the present invention a suitable manganese containingmelt, i.e., one containing 25 percent or more manganese, is prepared byany convenient technique. For example, certain commercially availablemanganesebearing materials, such as ores which have been calcined tonodules can often be fused with lime, in the absence of carbon, toprovide a suitable oxygen-depleted melt. With other materials such asraw manganese ores, carbon can be admixed with ore and lime and themixture smelted, for example in a submerged arc electric furnace, toprovide the required oxygen level in the melt. The carbon admixed withthe ore can be in any suitable form, including coal and the lower gradesof coke, and is preferably present in an amount to reduce substantiallyall of the manganese values to the manganous, i.e. divalent state, butnot to the elemental state. Also, by-product manganese-containing slagscan be used. Regardless of the manner in which it is obtained, the lowoxygen content is required in the manganese-containing melt so that thesubsequent ladle reaction is controllable and not excessively violent.

When a suitable low oxygen, manganese-containing melt has been prepared,preferably containing between about 25 to 50 percent manganese, whichcan be accomplished, for example using a smelting furnace such asindicated schematically as 10 in the process diagram of FIGURE 1, themolten material, at a temperature of about 1350 to 1800 C is transferredinto a ladle as indicated at 12. A molten silicon reducing agent, in thetemperature range of about 1250 to 1450 C., preferably one containing4-32% silicon, 60 to Mn, 0.03 to 1.6% C balance Fe, is also introducedinto the ladle with the result that a metal phase is provided at thelower portion of the ladle as indicated at 16 with the manganesecontaining oxidic melt floating on top as indicated at 18. The amount ofsilicon reducing agent in the ladle is that which is sufiicient toprovide reduction of manganese values in the oxidic melt to provide thedesired ferromanganese alloy. Limecan also be added to the ladle and isusually present in an amount that will provide a base-toacid ratio offrom 0.1 to 1.6 in the final slag Percent CaO-l-Percent MgO Percent SiOGenerally, the starting ratio of oxidic material to metal ranges from1:1 to 4:1 by volume. With suitable amounts of manganese-containingoxidic material, silicon reducing agent and lime in the ladle, gas,under pressure is introduced below the surface of the metal phase, andthe velocity adjusted until turbulence is developed in the metal phasewhereby metal is forced upward through the manganese-containing oxidicmaterial and falls back down through the manganese-containing oxidicmaterial. This condition can be readily achieved by slowly increasingthe gas input and observing the surface of the material in the ladle.When it is observed that portions of molten metal are being forced upthrough the layer of oxidic material and pass back down through theoxidic material, in a steady, rapid, but not unbroken succession the gasinput is sufiicient; at lower gas inputs, the improved resultshereinafter described are not obtained due to insufficient mixing of theprocess reactants. Also, if the gas pressure is increased to the extentthat a blast, i.e., a continuous stream of gas passes up through themetal and oxidic material, the results are also unsatisfactory in thatin- Sllfi'lClfiIlt mixing is obtained. That is to say, in the presentinvention, an essentially intermittent passage of gas is required.

The mechanism of the aforementioned gas agitation is to promote acontinuously changing contact between the silicon-reducing agent and themanganese-containing oxidic material whereby manganese is reduced by thesilicon and passes into the metal phase and silicon is converted tosilica and combines in an oxidic slag phase.

The gas agitation is continued until the reduction reaction isessentially complete which can be determined for example by analyzingsuccessive samples of the metal phase so as to observe when equilibriumis reached. When the reduction reaction is completed, the oxidic, i.e.,slag phase is decanted from the ladle andeither thrown away or re-useddepending upon the manganese content, and the metal phase can be castinto molds.

To illustrate the particular advantages of the present invention, aseries of tests were conducted using the gas: mixing procedure of thepresent invention and the previously knownrepouring technique to producemediumto-low carbon ferromanganese (70-90% Mn, 0.041.5% C, 01-14% Si,bal. Fe).

In practicing the present invention, a ladle of the type shown in FIGURE2 was employed. This ladle comprises an outer shell 20 formed of steel,a refractory lining of rammed periclase and magnesia 22, a refractorybase of rammed magnesia 24, and a tuyere 26, which is surrounded by acore arrangement 28 suitably formed of a castable alumina refractorymaterial such as Purotab Tuyere 26 is suitably formed of stainless steeland gas is passed through hose .30 via tuyere 26 into the ladle.

The following examples will further comparatively illustrate thebenefits of the present invention.

Example Molten silicon reducing agent (Mn 65%, Si 18%, C 1.6%, bal. Fe)in the amount of 780 pounds at a term perature of about 1300 'C. waspoured into a ladle of the type shown in FIGURE 2. The dimensions of theladle were inner diameter 2.5 feet, height 3.0 feet. A moltenmanganese-bearing oxidic material (MnO 36.6%, CaO 25.7%, MgO 2.9%, Al O8.1%, Si 26%) in the amount of 1100 pounds at a temperature of about1500 C. was poured into the ladle. With the aforementioned materials inthe ladle, molten metal. filled the lower 0.42 feet of the ladle and themolten metal phase was covered by about 1.08 feet of oxidic material. Aspace of about 1.5 feet remained empty at the top of the ladle. Argongas under pressure was through a tuyere, 0.125

until vigorous agitation of the ladle contents occurred and molten metalwas continually heaved above the sur' face of the oxidic material, andfell back down through the oxidic. material, *but did not causesignificant splash ing of material out of the ladle. The gas flow forthis condition was about 215 s.c.f.h.

The gas fiow was which the oxidic slag material and the molten werepoured into a magnesia lined pot.

The recovered metal (852 lbs.) analyzed 74% Mn, 11.2% Si, 1.4% C, bal.Fe; the manganese content of the slag material was 17.2%; andthebase-to-acid ratio of the slag was 0.88. The ratio by weight of metalproduct to slag was 0.88 to 1 and the overall recovery of manganese was97.4%.

The above procedure was repeated in additional tests in which thematerials and processing conditions were essentially the sameexcept forthe lime content of the charge which was varied to provide base-to-acidratios metal phase 1 Available from Kaiser Refractories Co.

introduced into the molten metal inch in diameter, centrally located atthe bottom of the ladle and the gas flow was increased.

continued for about 10 minutes after t Fifteen further tests wereconducted in which the ma- 7 terials and processing were essentially thesame except (1) that the lime content of the charge was varied toprovide base-to-acid ratios ranging from 0.1 to 1.6 and (2) thatre-pouring was used instead of gas agitation. The repouring techniqueinvolved pouring the contents of the first ladle into a substantiallyidentical second ladle, repouring back to the first ladle, and then onceagain re-pouring from the first to the second ladle. In all instancesthe alloy product was medium-to-low carbon ferromanganese containing 72to 78% Mn, 6 to 12% Si, 1.1 to 1.5% C, bal. Fe.

The results of the aforesaid tests, based on the baseto-acid ratio andunreduced manganese retained in the slag are shown in the graph ofFIGURE 3.

As can be seen, the graph of FIGURE 3, for a baseto-acidratio of 1.0,almost,50% more manganese is recovered using the gas mixing practice ofthe present invention as compared to the previously standard re-pouringtechnique (14% Mn in slag compared to 20%).

From another point of view, to obtain a slag containing a particularmanganese, .e.g., 20% Mn, a much lower base-to-acid ratio can be usedwith the present invention, as compared to re-pouring. This means thatsubstantially less lime isrequired and consequently a larger volume ofmetal can be produced in a given ladle. Also, with the use of less lime,less manganese metal is entrapped in the slag phase and hence manganeserecovery is higher.

Since the present invention involves the mixing of molten phases ofdifferent densities to promote the interreaction thereof, and is not arefining or gas-reaction process wherein gas is a significant processreactant, a rather wide variety of non-reactive gases can be etfectivelyemployed. For example, all of the inert gases can be used and air canalso be used since the temperatures and gas velocities involved do notlead to any significant re-oxidation of manganese. Nitrogen, carbonmonoxide and carbon dioxide can also be used eifectively..

What is claimed is:

1. A process for the production of manganese-containing alloys whichcomprises providing in a ladle a melt of oxidic manganese-containingvmaterial in which the amount of oxygen combined with manganese is nogreater than about that represented by the formula Mn O together with asilicon reducing agent to thereby provide a molten metal phase in thelower portion of the ladle and molten oxidic manganese-containingmaterial floating on and covering the metal phase, and reacting themolten metal and oxidic material by introducing gas under pressure intothe molten metal phase to cause turbulence in the metal phase thepressure of the gas being suflicient to cause intermittent passage ofgas through the molten metal and oxidic phase and being at a ratesufiicient to cause a portion of molten metal to be continually forcedupward through the oxidic phase in a steady, rapid, but not unbrokensuccession and to fall back downward through the oxidic phase.

2. A processfor the production of medium-to-low car bon ferromanganesecomprising providing in a ladle a melt of oxidic manganese-containingmaterial in which substantially all of the manganese values are in themanganous state together with a molten metal reducing agent containingbetween about 4 and 32 percent silicon to provide a molten metal phasein the, lower portion'of the ladle and molten oxidic material floatingon and covering the metal phase, and reacting the molten metal andoxidic material by introducing gas under pressure into the metal phaseto cause turbulence in the metal phase the pres sure of the gas beingsufilcient to cause intermittent passage of gas through the molten metaland oxidic phase and being at a rate sufficient to cause a portion ofmolten metal to be continually forced upward through the oxidic 5 6phase in a steady, rapid, but not unbroken succession and 3,015,554 1/1962 Rummel 7560 to fall back downward through the oxidic phase.3,025,047 3/1962 Reinfeld et a1 266-34 3,057,616 1 0/ 196 2 Wohlfahrt eta1. 75-6 0 References clted 3,058,822 10/1962 Volianik 75-429 UNITEDSTATES PATENTS 3,074,793 1/19'63 Kuhlmann 75133.5 7 1942 Heller 75 933,084,039 4/1963 Baum v 75-59 6/1956 'Perrin 75-133,5 ,1 24 4/1964Spolders et a1 2/6'634 7/1956 Spire 75--51 3,138,455 6/1964 Carosella eta1. 75--133.5 9/1959 Kalling et a1. 7560 11/ 196 0 Morrill 7560 10BENJAMIN HENKIN, Primary Examiner.

311321 111231 151;313:3111: 32-23 DAVID RECK,

1. A PROCESS FOR THE PRODUCTION OF MANGANESE-CONTAINING ALLOYS WHICHCOMPRISES PROVIDING IN A LADLE A MELT OF OXIDIC MANGANESE-CONTAININGMATERIAL IN WHICH THE AMOUNT OF OXYGEN COMBINED WITH MANGANESE IS NOGREATER THAN ABOUT THAT REPRESENTED BY THE FORMULA MN2O3 TOGETHER WITH ASILICON REDUCING AGENT TO THEREBY PROVIDE A MOLTEN METAL PHASE IN THELOWER PORTION OF THE LADLE AND MOLTEN OXIDIC MANGANESE-CONTAININGMATERIAL FLOWING ON AND COVERING THE METAL PHASE, AND REACTING THEMOLTEN METAL AND OXIDIC MATERIAL BY INTRODUCING GAS UNDER PRESSURE INTOTHE MOLTEN METAL PHASE TO CAUSE TURBULENCE IN THE METAL PHASE THEPRESSURE OF THE GAS BEING SUFFICIENT TO CAUSE INTERMITTENT PASSAGE OFGAS THROUGH THE MOLTEN METAL AND OXIDIC PHASE AND BEING AT A RATESUFFICIENT TO CAUSE A PORTION OF MOLTEN METAL TO BE CONTINUALLY FORCEDUPWARD THROUGH THE OXIDIC PHASE IN A STEADY, RAPID, BUT NOT UNBROKENSUCCESSION AND TO FALL BACK DOWNWARD THROUGH THE OXIDIC PHASE.